The invention relates to a device for holding a lever, which can pivot or rotate with the device about a rotational axis, wherein the device is spaced apart from the rotational axis and can rotate or pivot with the lever about the rotational axis.
The subject matter of the invention relates to devices for measuring reaction moments and forces on a lever. The levers are formed, for example, as measuring beams. In this case, the measuring beams are components of the measurement device, especially for measuring torques in rotating connections. Alternatively, the levers are sections of shafts or sections on articulated shafts, which are connected in an articulated way to another section via a joint. The reaction forces or reaction moments develop as reactions to torques in rotating connections or in bearings or to bending moments in joints, when rotating connections or bearings are turned or joints are bent.
The moments of rotating connections are, for example, the torques that develop from friction and/or rolling contact in the rotating connection when two components supported so that they can rotate one on the other or one in the other, for example, the inner ring and the outer ring of a roller bearing, slide one on the other or are supported relative to each other on roller bodies arranged in-between. Here, the lever is turned about the rotational axis at least once 360°. As a rule, the torques of roller bearings should be as low as possible.
In articulated shafts of the drive train of vehicles, the bending moment is a measure for the prevailing play in the joint arrangement. However, for example, in so-called constant-velocity joints, especially in pin universal joints, the play is an evaluation criterion for the function of the articulated shaft arrangement. Unbalanced masses around the rotational axes of the articulated shaft sections can develop due to play that is too great.
The resistance at the folding point of a joint is designated as the bending moment, which is directed opposite the bending of two articulated shaft sections connected to the joint and can be detected and thus can be measured. The bending moment is dependent on the construction of the correspondingly hinged connection and is comprised, for example, from friction moments and from other resistance of the roller contact at a joint of an articulated shaft of a motor vehicle. In pin universal joints, the value of the bending moment is set at the freedom of play of the joint, i.e., the joints are installed intentionally with pre-tensioning. Friction is intentionally set, for example, between the ends of the pin joint and the bases of the universal joint bushings. Pin universal joints are hinged connections transmitting torques between two articulated shaft sections without play as much as possible in all directions. In pin universal joints, each of the articulated shaft sections is provided with a joint yoke. The two joint yokes are connected by means of a universal joint so that they can pivot about two joint axes and are supported usually with low friction as much as possible on the pin of the universal joint by roller bearings. Each of the joint axes (bending axes) corresponds to one of the pin joint axes, which are oriented perpendicular to each other and which cross at the center of the universal joint. With the measurement of the bending moment, this resistance can be tested together with other resistances, for example, from the radial roller bearings of the universal joint bushings. For this purpose, a joint section of the articulated shaft arrangement is fixed and the other pivots about one of the axes of the pin joint.
With constant-velocity joints, a hinged connection, which transmits torques and which must allow relative axial movements between the articulated shaft sections, is produced between two articulated shaft sections. For this purpose, the joints usually feature roller bodies, which are guided in raceways and on which the two joint sections roll relative to each other so that they can move in the axial direction and via which the joint sections are engaged with each other to transmit torque with a positive fit in the peripheral direction. The friction moments should be as small as possible in this arrangement.
Small play in joint arrangements is important for the function of the articulated shaft. Because the constant-velocity joints should allow axial compensation, the play is positive. Positive plays are air gaps between elements supported one on the other. These plays should be as small as possible, but should also be provided to keep the bending moments small. In contrast, in pin universal joint arrangements, the pin joint and the joint yokes are mounted, as already mentioned above, so that they can move relative to each other, without play, and with pre-tensioning. In order to guarantee freedom of play, the elements are preferably mounted relative to each other with negative play, that is, with pre-tensioning. A measure for the freedom of play or the measure for the pre-tensioning, with which the joint yokes and the pin joint are to be mounted or are assembled with each other is the bending moment, with which the pre-tensioned joint can bend about the respective joint axis. The bending moment necessary for the functioning of each articulated shaft arrangement is first determined and fixed with reference values. The reference values are then added, for example, for quality control purposes for comparison with mass-produced products.
DE 39 22 194 C1 describes a method and a device of the most general form for measuring bending moments in pin universal joint arrangements. The device is formed by a holder, with which an articulated shaft section is held stationary. The joint yoke of this joint section is oriented in the device so that the other articulated shaft section is driven by the pivot drive so that it can pivot about the joint axes of the pin joint. A bending rod, whose fibers of the outer skin are elongated or compressed as a function of bending direction and resistance of the joint, is arranged between the pivoting joint section and the pivot drive. Expansion measurement strips, with which the expansion of the fibers is detected and converted into corresponding electrical voltage magnitudes, are arranged on the outer skin.
The pivot drive is connected in an articulated way to a radial guide and then via a ball-and-socket joint to the bending rod. The radial guidance can pivot with a pivoting angle of 90° about the rotational axis of the articulated shaft arrangement in the sense of rotation by means of the pivot drive.
With the method described in DE 39 22 194 C1, counteracting bending moments about the two joint axes when the moving joint section bends relative to the rigid joint section are measured. For this purpose, the radial guidance is pivoted about the rotational axis on an arc by 90° in the sense of rotation by means of the pivot drive. Here, the counteracting bending moments on the joint axes are first detected in the form of tension magnitudes on the expansion measurement strips of the bending rod. These tension magnitudes are proportional to the bending moments, are recorded, and are selectively converted and displayed legibly in a display device.
DE 41 02 278 A1 shows and describes a device for measuring forces and moments in articulated shaft arrangements with constant-velocity joints. This device has a stationary receptacle, in which one of the joint sections is held rigidly. The other articulated shaft section can pivot relative to the fixed articulated shaft section by means of the joint. A device for measuring the force-path, in which the pivoting articulated shaft section is held, is arranged on the pivot axis between the contact of the pivot drive and the joint. The receptacle, in which the pivoting articulated shaft section is held, is movable with the articulated shaft section. Radial movements and pivoting movements are converted at force-path sensors (force measurement sensors) into corresponding signals, which represent the bending moment on the joint. The bending moments are translated as deflections of the receptacle, which are caused in the device by reaction forces to the moments on the bearing.
If the pivoting articulated shaft section is bent and simultaneously pivoted about the rotational axis, due to tolerance-specific dimension, shape, and position deviations from the desired values in the articulated shaft arrangement and/or the device, the effective measurement distance between the pivoting drive and the joint or between the receptacle in the measurement block and the pivot drive is changed as a function of the bending angle or an attempt to realize this change. This can lead to axially directed constraining forces in the arrangement. Both the distance changes and also the constraining forces can falsify the measurement results. Shape and position changes, for example, deviations of the concentricity of the rotational axes of the articulated shaft sections or alignment errors between the rotational axes and the longitudinal axis of the receptacle in the measurement block, can lead to alternating constraining forces, for example, twisting of the articulated shaft section in the device. In other cases, the play between the receptacle and the articulated shaft section can be too large, so that the articulated shaft is movable for measurements within the play in the device with the corresponding disadvantageous effects on the measurement result.